Airbnb·Software Engineer·Technical Phone Screen
Jul 2026
Airbnb software engineering interview that was basically a full game engine design problem. More depth than I expected for a single session, covering API design, win detection optimizations, and extensibility all in one go.
- Design and implement a Connect Four game engine that supports an arbitrary m×n board and a configurable k-in-a-row win condition. The API should include a constructor, a move method returning win/draw/invalid status, and a separate isDraw method.
- How would you implement win detection across all four directions (horizontal, vertical, and both diagonals) efficiently, ideally in O(1) or near-O(1) time per move? What data structures support this?
- What is the time and space complexity of your solution?
- How would you extend the design to support a reset() method and an optional undo() operation efficiently?
- How would you test this game engine, specifically around edge cases like full columns, out-of-range column inputs, and wins that happen earlier than expected?
“The generalized board part tripped me up at first.” The rest of the author's notes on Software Engineer interview at Airbnb, Technical Phone Screen round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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